Process Loads

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I have a question about definition and correct interpretation. If I am
modeling building that has a space with a data rack and its own cooling
system separate from the rest of the buildings systems, is the cooling
considered process energy because it is "required" to be there similar to
the data rack electrical energy?

thanks in advanced,

--
Rob Hudson

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Rob,

You can try but I really doubt if the reviewer will see it that way. I
always consider it its own HVAC system in the proposed model and lump it
in with the one system per floor HVAC system in the baseline model.

I do not see much of a benefit for counting this as a process load,
maybe you can explain why you want to do this.

Otto

Otto Schwieterman's picture
Joined: 2011-09-30
Reputation: 200

Assuming we're talking about 90.1, the definition for process load reads
something like "loads that don't have anything to do with HVAC..." so
you could make the case that a small IT closet split DX unit or
thermostat-controlled exhaust fan is not a process load, and therefore
the HVAC must be modeled as a system. Why would one want to do this?
You could demonstrate better performance with your efficient (?) system.

On the other hand, loads in small IT closest are commonly core zones
with 24/7 loads, and as a result any such system would be running 24/7
and/or on a consistent basis. An offshoot is you could very simply roll
any A/C for such spaces into the room's W/SF, and there would
potentially be little difference in consumed energy modeled. Why would
one want to do this? Objectively: It's easy/fast.

If those were the only two points of interest on the table, as your
reviewer I wouldn't care either way.

That said, the two above paths result in a pretty different baseline
scenario: On the one hand you end up with a baseline system against
which your proposed system may excel or underperform against in handling
the data/IT room's heat loads. In the other case you have zero direct
conditioning of the loads in that space in either model, which would
have to propagate into adjacent spaces/systems via partitions - which is
in most cases a step or two away from reality. Where one approach is
"removed" from reality and the other may objectively "reward/punish" the
design decisions made to condition that space, I think it's pretty clear
which is the preferable judgment from a reviewer's standpoint.

Then again, I'm not your reviewer ;).

NICK CATON, E.I.T.

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also note that if you're dealing with a small IT closet, or data room,
90.1 applies to comfort cooling applications. i.e. people comfort, not
machinery comfort. try getting a liebert unit per the efficiency
requirements of 90.1 chapter 6. probably won't happen. if you're just
dealing w/a small IT closet or small data room and it is served by a
packaged dx system i've just put them in both the proposed and baseline
since it constitutes a single thermal zone.

but as far as process loads go, i typically include it/data in process
loads & haven't had that questioned yet. it does, after all, add to the
total process that reviewer's look for being 25% of the baseline
building cost.

Patrick J. O'Leary, Jr.'s picture
Joined: 2011-09-30
Reputation: 200

So, if i have a large IT space with numerous data racks, the HVAC system
could fall into the G3.1.1 Exception b that states that since it is
thermally different than all other spaces around it, it can be modeled as
its own system in the baseline model. This would reward/penalize as you
guys are saying.

Now, to further the other part of the discussion, the definition of process
energy stats any energy consumed in support of processes other than
conditiong spaces and maintaining comfort and amenities for the occupants.
This HVAC system would be maintaining "comfort" even though there is no
occupants in the space?

Thanks for all the help guys, hope your monday is treating you well.

Rob

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